Electron dynamics surrounding the X line in asymmetric magnetic reconnection. Issue 7 (21st July 2017)

• Record Type: Journal Article
• Authors: Zenitani, Seiji; Hasegawa, Hiroshi; Nagai, Tsugunobu
• Is Part Of: Journal of geophysical research. Volume 122:Issue 7(2017)
• Page Start: 7396
• Page End: 7413
• Publication Date: 2017-07-21
• Subjects: magnetic reconnection -- particle dynamics -- PIC simulation -- magnetopause -- plasma mixing; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2017JA023969
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Electron dynamics surrounding the X line in magnetopause‐type asymmetric reconnection is investigated using a two‐dimensional particle‐in‐cell simulation. We study electron properties of three characteristic regions in the vicinity of the X line. The fluid properties, velocity distribution functions (VDFs), and orbits are studied and cross‐compared. On the magnetospheric side of the X line, the normal electric field enhances the electron meandering motion from the magnetosheath side. The motion leads to a crescent‐shaped component in the electron VDF, in agreement with recent studies. On the magnetosheath side of the X line, the magnetic field line is so stretched in the third dimension that its curvature radius is comparable with typical electron Larmor radius. The electron motion becomes nonadiabatic, and therefore the electron idealness is no longer expected to hold. Around the middle of the outflow regions, the electron nonidealness is coincident with the region of the nonadiabatic motion. Finally, we introduce a finite‐time mixing fraction (FTMF) to evaluate electron mixing. The FTMF marks the magnetospheric side of the X line, where the nonideal energy dissipation occurs. Key Points: Electron velocity distribution functions are analyzed using a subset of 2‐D PIC simulation trajectories Electron nonadiabatic motion violates the ideal condition Finite‐time mixing fraction is proposed to diagnose the electron‐mixing behavior